Standing valve for free well pump



July 3, 1962 c. J. coal-:RLY

STANDING VALVE FOR FREE WELL PUMP Original Filed Feb. 10, 1955 2 Sheets-Sheet 1 llllllllllll im H ci www@ Ef MH, S QM@ e@ m July 3, 1962 c. J. coal-:RLY

STANDING VALVE FOR FREE WELL. PUMP Original Filed Feb. l0, 1955 2 Sheets-Sheet 2 United States Patent Ottico 3,l,98l Patented July 3, 1962 3,641,981 STANDING- VALVE FOR FREE WELL PUMP Clarence 3. Coberly, San Marino, Calif., assigner to Kobe,

Inc., Huntington Park, Calif., a corporation of California 4 Clanes. (el. 10s-229) The present invention relates in general to well pumps and, more particularly, to standing valves for such pumps,

this application beinga division of my application Serial No. 487,303, tiled February 10, 19'55, now Patent No. 2,869,470, issued January 20, 1959, and being a continuation of my co-pending application Serial No. 639,497, tiled February ll, 1957, now abandoned. For convenience, the standing valve of the present invention will be considered herein in the environment disclosed in said patent with the understanding that it may be utilized in other environments also.

A primary object of the invention is to provide a standing valve or lstanding valve assembly forwell pumps which includes an upwardly opening check valve adapted to be closed 4by the action of gravity and which includes fluid means for retarding closing or sealing of the check valve so that it does not close or seat during normal operation of the well pump with which it is associated at the minimum speed of operation of the pump, even though the pump is a single-acting pump, or a doubleacting pump one end of which fails to operate for some reason.

Prior standing valves incorporate check valves which are held off their seats by magnets during normal operation of the Well pumps with which they are associated. In such a standing valve assembly, only a high back flow of fluid into the well will pull the check valve away from the magnet and cause it to seat. `Severe hydraulic shock loads may be introduced when the check valve of such a prior standing valve assembly seats in this fashion, which is a disadvantage, particularly in deep wells.

With the present invention, wherein the check valve is not held open by a magnet and wherein gravity-induced closing thereof is retarded hydraulically, no hydraulic shock loads are introduced upon seating, which is an important feature.

Another object of the invention is to provide a standing valve wherein the desired slow closing of the check valve is produced by restricting fluid flow which permits the check valve to close.

The foregoing objects, advantages and features of the present invention, together with various other objects, advantages and features thereof which vwill become apparent, may be attained with the exemplary embodiment of the invention illustrated in the accompanying drawings and described in detail hereinafter. Referring to the drawings:

FIG. l is a vertical sectional view on a reduced scale illustrating a fluid-operated free pump system which embodies the invention;

FIG. 2 is a sectional view taken along the arrowed line 2 2 of FIG. 1;

FIG. 3 is a vertical sectional view taken along the arrowed line 3-3 of FIG. 2;

FIGS. 4 and 5 are downward continuations of FIGS. 3 and 4, respectively;

FIG. 6 is a vertical sectional view taken `along the arrowed line 6-6 of FIG. 2;

`FIGS. 7 and 8 are enlarged, fragmentary sectional views duplicating a portion of FIG. 3, but illustrating the latch means of the invention in different operating positions;

FIG. 9 is an enlarged, fragmentary sectional view illustrating means for mechanically resetting the latch means of the invention;

FIG. l is a view of one end of the latch means of the invention; FIG. ll is a view of the other end of the latch means;

and

FIG. 12 is an enlarged, fragmentary vertical sectional view duplicating a portion of FIG. 5 on a larger scale.

Referring particularly to FIG. l of the drawings, the numeral 12 designates a well casing which is set in a well and which is provided with perforations, not shown, to admit into the casing fluids from surrounding, productive formations. The casing 12 is equipped with a casing head 14 which supports parallel production and supply tubings 16 and 18 in the casing, these tubings extending downwardly below the well fluid level in the casing. The production and supply tubings 16 and 18 communicate at their upper ends with a four-way valve 20 operated by a handle 22, this valve selectively connecting the production tubing and the supply tubing with an operating iluid supply line 24 and a production iluid disposal line 26. Thus, by means of the valve 20, either the production tubing 16, or the supply tubing 18, may be pressurized with operating iluid from the supply line 24.

In accordance with the invention, the production tubing 16 is of relatively large diameter to accommodate a iluidoperated free pump unit 28 which may be insertedinto the upper end of the production tubing by removing a closure 3l) which may contain the usual free pump catcher. The pump unit 28 is circulated downwardly through the production tubing 16 by connecting the upper end of the production tubing to the supply line 24 until the pump unit arrives at its operating position in a housing which is designated generally by the numeral 32 and which is an assembly of components to be described in more detail hereinafter. The housing 32 is connected to the lower end of the production tubing 16 and is also connected to the supply tubing 18, all as will be discussed in more detail hereinafter.

The pump unit 28 includes a pump 34 to the upper end of which is connected a packer nose 36. The pump 3'4, except for minor external modifications, may be of any suitable type, such as that shown in my Patent No. 2,311,157, granted February 16, 1943, or in my Patent No. 2,338,903, granted January l1, 1944, and contains the usual pump and engine, or motor, sections together with valve means for controlling the operation of the engine, or motor, section. The latter includes a motor piston which reciprocates a pump piston in the pump section to pump well fluid from the well and discharge it as production fluid in a well known manner. Since such components of the pump 34 are well known in the art, they are not illustrated in the drawings and are not described further herein.

Referring now to FIG. 5 of the drawings, the housing 32 includes at its lower end a bottom shoe 148 providing a seat 38 for a standing valve assembly 40 which extends downwardly into an intake pipe 412 depending from the bottom shoe. Well iluid enters the pump 34 through the standing valve assembly 40, which will be described in more detail hereinafter. The lower end of the pump 34 is provided with a tubular well-Huid intake 44 which is insertable into a bore 46 in the standing valve assembly 40, the intake 44 carrying an 0-ring 48 which engages the wall of the bore 46 to provide a seal which prevents entry of well fluid into the housing 32 except through the wellfluid intake.

Continuing to refer to FIG. 5 of the drawings, communicating with the interior of the housing 32 above the 70 standing valve assembly 40 is a port St) which communicates, in turn, with a passage 52 in the bottom shoe 148.

The passage 52 communicates at its other end with a pipe 54 which extends upwardly into communication with the lower end of a passage 56, FIG. 4, in a sealing collar 146 forming part of the housing 32. The upper end of the passage 56 communicates with the lower end of the supply tubing 18. Thus, operating fluid may be delivered through the supply tubing 1-8, the passage 56, the pipe 54, the passage 52 and the port 50 to the lower end of the pump 34 to unseat the pump unit 2S, i.e., withdraw the well-fluid intake 44 from the bore 46, and move the pump unit'upwardly from the housing 32 into the production tubing 16, as will be described in more detail hereinafter. As will be apparent, the O-ring 48 maintains separation between the well fluid in the standing valve assembly 40 andthe operating uid in the housing 32 at the lower end of the pump 34.

Referring to FIG. 4 of the drawings, the passage 56 communicates intermediate its ends with a port 53 in the sealing collar 146, the latter communicating with the interior of the sealing collar. The pump 34 is provided with operating-fluid inlet ports 60 which communicate with the port 58 when the pump unit 28 is in its operating position. Thus, in order to operate the pump 34, operating fluid under pressure delivered to the supply tubing 18 llows downwardly through the supply tubing, the passage 56 and port 58 to the operating-fluid inlet ports 60. The latter are isolated by O-rings 62 and 64 engaging a sleeve 65 in the sealing collar 146 to prevent intermingling of the operating fluid under pressure with the production uid and the spent operating fluid, as discussed in more detail hereinafter.

Referring now to FIG. 6 of the drawings, the pump 34 is provided with outlet ports 66 for spent operating liuid and discharge ports, not shown, for the production fluid discharged by the pump. Both the outlet ports 66 and the discharge por-ts communicate with the interior of a pump housing tube 150 intermediate the O-ring 64 and an 0- ring 67 engaging a sleeve 68 in the bottom shoe 148, the tube 150` forming part of the housing 32 and connecting the sealing collar 146 and the bottom shoe 148, as hereinafter explained. Thus, the O-ring 67 separates the mixture of. spent operating fluid and production fluid from the operating fluid at the lower end of the pump, and the O-ring 64 separates the mixture of spent operating iluid and production fluid from the operating uid in the vicinity of the operating-fluid inlet ports 60. 4

The mixture of spent operating fluid and production fluid flows thro-ugh the tube 150 between it and the pump 134 to a port 70 in the bottom shoe 148, as shown in FIG. 6 of the drawings. The port 70 communicates with a passage 72 in the bottom shoe 14S which communicates at its other end with a pipe 74 leading upwardly to the lower end of a passage 76 in the sealing collar 146, the upper end of the latter communicating through a port 78 with the interior of the sealing collar above the 0- ring 62. Thus, the O-ring 62 separates the operating fluid under pressure supplied to the operating-duid inlet ports 60 from the mixture of spent operating fluid and production fluid entering the sealing collar 146 above the O-ring 62 by the avenue outlined. The interior of the sealing collar 146 above the O-ring 62 communicates with the lower end of the production tubing 16 through a packer housing tube 90, which forms part of the housing 32, to provide for upward flow of the mixture of spent operating fluid and production Huid therethrough to the surface.

When the pump unit 28 is in the housing 32 with the well-fluid intake 44 in the bore 46, the area of the wellfluid intake 44 is exposed to well Huid pressure and, with operating fluid pressure applied to the supply tubing 1S, such operating fluid pressure plus the head of operating fluid are applied to an area of the pump 34 equal to the difference between the area of the pump at the sealing collar 146 and the area of the well-fluid intake 44. Both the well fluid pressure and the operating iiuid pressure applied to such areas of the pump act upwardly on the pump unit 28. Acting downwardly on the pump unit over the area of the pump at the sealing collar 146, is the discharge pressure in the production tubing 16, which is equal to the head of the mixture of spent operating uid and production fluid in the production tubing. When the pump 34 is in operation, the net result of the foregoing pressure applications to the pump unit is the application of an upward bias to the pump unit tending to move the pump upwardly into the production tubing 16, which, as described in more detail hereinafter, is utilized to circuate the pump to the surface. However, when the pump 34 is in operation, the pump unit 28 is held in its operating position in the housing 32 in opposition to such upward bias by a latch means St) of the invention which will now be described.

Considering the latch means 8@ generally, it includes a latch housing 82 which provides a 'latch guide 84 for latches 86 engageable with a downwardly facing annular shoulder 8 in the tube 90. Connected to the upper end of the latch housing l82 is a nose 92 which is engageable with a pump catcher carried by the closure 3i) as is well known in the art. Connected to the lower end of the latch housing 82 is a packer tube 94 which is connected to the upper end of the pump 34, the interior of the packer tube communicating with the operating-huid inlet ports 60 so that, when these ports are in communication with the port 58 and operating fluid under pressure is supplied to the supply tubing 15, operating fluid under pressure is also present in the packer tube 94 for a purpose to be discussed. The packer tube 94 carries downwardly facing packers 96 and 98 which are disposed in enlarged portions 10i) and 162, respectively, of the tube when the pump uuit 23 is in its operating position, whereby the mixture of spent operating fluid and production fluid may ow upwardly past the packers 96- and 98 into the production tubing 16. It will be noted that a clearance is provided between the latch housing 82 and the tube 96 for such upward flow of the mixture of spent operating fluid and production fluid. Above the lower packer 96 is a reduced portion 104 of the tube 90 with which the lower packer 96 is engageable after the pump has been unseated in a manner to be described, the lower packer thus forming a seal with the reduced portion 14 so that operating iiuid pressure applied beneath the pump will move the pump unit 28 upwardly in the housing 32. By the time the lower packer 96 reaches the upper end of the reduced portion 164 of the tube 90, the upper packer 93 will be within and making a seal with the production tubing 16 to continue the upward movement of the pump. Ultimately, of course, both the packers 96 and 98 will engage and make seals with the production tubing 16 to enable the operating Huid under pressure de- `livered below the pump 34 for the purpose of circulating the pump unit 2S out of the hole, to perform its intended function.

Considering the latch means S0 now in more detail, the latch guide 84 has` the form of a transverse cylindrical bore through the latch housing 82, and the latches 86 have the form of pistons which are slidable in such bore and which are sealed relative to the wall thereof by O-rings 166. The ends of the latches 86 are reduced in diameter slightly and are provided with dats 107, as best shown in FIG. 11. rthe purpose of this diameter reduction is to permit latch retraction even with a build-up of foreign matter on the outer ends of the latches in use. The two latches 86 are identical, but reversed in position, one dat 107 on each being engageable with the shoulder 88.

As will be apparent, the outer ends of the latches 86 are exposed to the fluid pressure prevailing in the tube 96 surrounding the pump unit 28, i.e., the outerrends of the latches are exposed to the uid pressure in the production tubing 16. The inner ends of the latches 86 are adapted to be exposed to operating fluid pressure in the packer tube 94 through passages 108 connecting the interior of the packer tube to the interior of the latch guide 84. As

will be discussed hereinafter, when the latches 86 are fully retracted, FIG. 8, the O-rings 106 move across the ends of the passages S in communication with the latch guide 84 to prevent application of operating fluid pressure to the inner ends of the latches. The latch guide 84 also communicates with the packer tube 94 through a passage 11d, a chamber 112 anda passage 114. The passage 110 is adapted to be closed by a check valve 116 to prevent liow from the packer tube to the latch guide 34 by way of the passage 114, the chamber 112 and the passage 110. However, the check valve 116 is adapted to unseat to permit iiow in the opposite direction, i.e., to permit liow from the latch guide 84 to the packer tube 94 by way of the passage 1110, the chamber 112 and the passage 114. The reasons for this will be discussed hereinafter. The latches S6 are provided with inwardly extending spring fingers 113 having lateral projections 120 provided with inner edges 122 and outer edges 124 engageable with a pin 126 extending across the latch guide. When the latches 86 are in extended positions, as shown in FiG. 7 of the drawings, the inner edges 122 of the spring ngers 118 are out of engagement with the pin 126. However, the free ends o the spring iingers 118 still engage the pin 126 under such conditions to prevent rotation of the latches 86 in the guide Sd, When the latches are in an intermediate position, as shown in FIG. 3 ofthe drawings, the inner edges 122 of the lateral projections 120 engage the pin 126 to prevent `further inward movement of the latches except upon the application of a substantial pressure to the outer ends of the latches. When the latches are in their retracted positions, as shown in FIG. 8 of the drawings, the lateral projections 12d on the spring fingers 118 have moved across the pin 126 so that the outer edges 124 of such projections engage the pin to retain the latches in their retracted positions. It will be noted that, under such conditions, the lO-rings 106 on the latches 86 have crossed the ends of the passages 108 in communication with the latch guide '84 to prevent application of operating liuid pressure to the inner ends of the latches S6. Thus, once the latches 86 have been moved into their retracted positions, they cannot be hydraulically extended, for reasons which will be discussed hereinafter.

In order to prevent cocking of the latches 86 by lateral forces resulting from interengagement of the spring iingers 118 and the pin 126, the latches are provided with inwardly extending backup fingers 128. These lingers are provided with slots 130 therein which permit communication between the packer tube 94 and the latch guide 84 through the passages 108 until such time as such communication is cut off by the O-rings 106.

Considering the operation of the invention, prior to running the pump unit 28 into the well, the latches S6 are placed in their intermediate positions so that the inner edges 122 of the lateral projections 120 of the fingers 118 are seated against the pin 126. If the latches 86 are initially in their retracted positions, they may be extended to their intermediate positions by threading a screw 132 thereinto, as shown in FIG. 9 of the drawings. When in their intermediate positions, the latches 86 lare ilush with the pump body 34, as shown in FIG. 3 of the drawings. The spring fingers 11S are so designed that they will prevent inward movement of the latches 86 into their retracted positions except upon application of a substantial iiuid pressure, eg., 500 p.s.i., to the outer ends of the latches. The pressure required to move the latches 86 into their retracted positions must be higher than the pressure required to circulate the pump into its operating position, 500 p.s.i. being illustrative only.

With the latches 86 in their intermediate positions as hereinbefore described, the closure 30 vfor the upper end of the production tubing 16 is removed, the pump unit 2S is inserted into the upper end `of the production tubing, and the closure is replaced. Thereupon the valve is operated to connect the upper end of the production tubing 16 to the operating duid supply line 24, the valve simultaneously connecting the supply tubing 18 to the production duid disposal line 26. Preferably, the valve 20 is provided with some means, not shown, for limiting the operating fluid pressure applied to the production tubing 16 under such conditions to a value less than the pressure required to move the latches 86 into their retracted positions, so as to prevent retraction of the latches while the pump is being circulated into its operating position.

Under the foregoing conditions, the pump unit 28 is moved downwardly through the production tubing 16 into the housing 32, whereupon the well-fluid intake 44 at the lower end of the pump 34 enters the bore 46 in the standing valve lassembly 40, downward movement of the pump unit being terminated by engagement of a shoulder 134 at the lower end of the pump 34 with the upper end of the standing vaive assembly. It will be understood, that, as the pump unit 28 moves downwardly through the production tubing 16 into the housing 32, the tluid therebeneath is displaced upwardly to the surface through the supply tubing 1S, being directed from the supply tubing into the disposal line 26 by the valve` 2li.

The foregoing accomplished, the valve 2d is then operated to place the supply tubing .1S in communication with the operating-fluid supply line 24 and to place the production tubing 16 in communication with the productionfluid disposal line 26. A relatively low pressure, eg., 25 to 10G p.s.i., is slowly developed at the upper end of the supply tubing 1S, the valve 20 being operated slowly to prevent the development of a -pressure under the pump 34 sufiicient to unseat the pump unit 28 before the pressure in the latch means di? builds up enough to extend the latches S6. The relatively low pressure slowly developed in the supply tubing in the foregoing manner' is applied, through the packer tube 94 and the passages l108 connecting the packer tube to the interior of the latch guide 84, to the inner ends of `the latches 86 to displace these latches outwardly into their extended positions. Such a relatively low pressure, however, is insuiicient to move the pump unit 28 upwardly in the housing 32 `against frictional resistance as long as the pressure is Aallowed to build up slowly so as to minimize the pressure drop in the various passages leading to the inner ends of the latches.

Subsequently, normal operating fluid pressure is developed in the supply tubing 18 to operate the pump 34. When this occurs, the pump unit 28 moves upwardly in the housing 32 until the extended latches 85 seat against the shoulder 88 to limit upward movement of the pump unit, which is now latched in its operating position, shown in broken lines in FIGS. 3 and 5 of the drawings. The pump 34 now begins to operate to pump well fluid from the well by way of the well-duid intake 44 into the pro- Mduction tubing 16 by the avenue hereinbefore discussed.

The operating fluid for operating the pump 34 of course enters the pump through the operating-huid inlet ports 60 in the manner hereinbefore described, and the spent operating uid is mixed with the production duid and discharged into the production tubing 16, Ialso as hereinbefore discussed. The ydesired separation between iiuids is maintained by the various seals described previously.

When it is desired to remove the pump unit 28, the valve 2d is operated to again place the production tubing 16 in communication with the operating fluid supply line 24. 'lihe pressure in the production tubing 16 is then increased to a value in excess of that required to move the latches 86 inwardly through their intermediate positions into their retracted positions against the resistance oilered by engagement of the spring fingers 11S with the pin 126. The pressure necessary to move the latches into their retracted positions is determined by the stitiness of the spring fingers 118 and, as hereinbefore indicated, should exceed the pressure required to circulate the pump unit 28 into the hole. Also, this pressure should be more than any pressure diiierence resulting from the presence of water in the production tubing 16 which is only partially balanced by operating fluid in the supply tubing 1S. Upon :application of the required pressure to the outer ends of `the latches 86 by way of the production tubing 16, the latches S6 move inwardly to their retracted positions and are locked therein by engagement of the outer edges 124 of the lateral projections 120 on the spring fingers 113 with the pin 126. It should be noted that the check valve 116 opens to permit fluid in the latch guide 84 to be displaced into the packer tube 94, thereby permitting the latches to move inwardly into their retracted positions. Also, it should be noted that once the latches have been moved into their retracted positions in the foregoing manner, the O-rings 106 have crossed over the ends of the passages 103 in communication with the latch guide 84 to prevent any possibility of further application of pressure to the inner ends of the latches 86 tending to move them outwardly to their extended positions again as the pump unit 28 is circulated to the surface. The latches 86 may be reset later, after the pump unit has been removed from the production tubing 16, in any suitable manner, such as the manner illustrated in FIG. 9 of the drawings and `described previously.

Once the latches 86 have been retracted, the valve 20 is again operated to connect the supply tubing 18 in communication with the operating-fluid supply line 24 and to connect the production tubing 16 in communication with the production-fluid disposal line 26. Operating iluid under pressure is now delivered downwardly through the supply tubing 1S to move the pump unit 28 upwardly out of the housing 32 and through the production tubing 16 to the surface. As hereinbefore discussed, as soon as the pump unit moves upwardly slightly, the lower packer 96 engages the reduced portion 104 of the tube 90 to take the operating fluid pressure applied below the pump, the upper packer 98 shortly thereafter entering the lower end of the production tubing 16 to take the operating fluid pressure `applied below the pump vwhen the lower packer 96 enters the enlarged portion 102 of the tube 90. Eventually, both packers are in the production tubing 16 to carry the pump unit upwardly through the production tubing as operating fluid under pressure is delivered to the roduction tubing below the pump unit through the supply tubing. Once the pump unit 28 reaches the surface, it is caught by the pump catcher carrier by the closure 30, whereupon the closure may be removed to remove the pump unit. v

Considering the standing valve assembly 40 in more detail, it includes an upwardly opening check valve 136 of the poppet type adapted to engage a seat 138 and having a hollow stem 140l disposed in a damping cylinder 142. The check valve 136 is made light in weight and the fit between the stem 140 and the cylinder 142 is such as to give the desired rate of seating, the clear-ance between the stem and the cylinder restricting iluid into the cylinder above the stem to retard downward closing movement of the valve. Preferably, the rate of seating is sufficiently low so that the time required for the check valve to move from its fully open position to its closed position is in excess of ten seconds so that the check valve never seats while the pump 34 is in operation, even though the operating speed of such pump is very low. The clearance required to obtain this seating time with a standing valve of the proportions shown is approximately 0.010 inch, i.e., the difference in the diameter of the stem 140` and the cylinder 142 is approximately 0.010 inch. It should be noted that above the valve seat 13S the valve 136 moves through -a bore 144 which is only slightly larger than the valve so that there is only a relatively small clearance around the Valve until the valve has moved away from the seat 138 a substantial distance, e.g., one-half inch. The valve 136 must, therefore, travel at least this distance yfrom its operating position to its fully closed position, which, with the t specified be- 8 tween the stem and the cylinder 142, provides a Sullicient seating time.

Another `feature resides in certain aspects of the structure of the housing 32 providing for ease of assembly of various components thereof. Considering this feature, the housing includes the sealing collar y146 and the bottom shoe 148, into which the upper and lower ends of the pump housing tube 150 are threaded with extended threads and locked by means of lock nuts 152 and 154. Fluid-tight seals are provided between the ends of the tube 150 and the members 146 and 148 by O-rings 156 and 158, respectively.

The hereinbefore discussed pipes 54 and 74 are threaded into the sealing collar 146 with ordinary pipe threads, FIGS. 4 and 6, and extend into bores 160 and |162, respectively, in the bottom shoe 148, these bores forming parts of the passages 52 and 72, respectively. The lower ends of the pipes 54 and 74 are sealed in the bores and 162 by -O-rings 164 and 166, respectively, land the depths of the bores 160 and 162 exceed the totals of the distances which the respective pipes extend thereinto and into the sealing collar 146 when completely assembled. With this construction, the lower ends of the pipes 54 and 74 are inserted into the bores 160 and 162, respectively, and the members 146 and 148 and the tube y150 Iare then assembled and locked with the lock nuts 152 and 154. Under such conditions, the upper ends of the pipes `54 and 74 clear the sealing collar 146i, the upper ends of these pipes then being screwed into the sealing collar as shown. Upon assembly, the lower ends of the pipes 54 and 74 are sealed by the O-rings 164 and 166.

Although I have disclosed an exemplary embodiment of my invention herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiment without `departing from the spirit of the invention as delined by the claims allowed me and appearing hereinafter.

I claim:

l. In a standing valve assembly for a free well pump, the combination of: `a valve body providing a seat and a closed cylinder coaxial with said seat; a valve engageable with said seat and having a coaxial stem slidable in said cylinder, there being a flow restricting clearance between said stem and said cylinder; and a wall on said valve body coaxial with said seat and said cylinder and extending axially away from said seat in the direction of opening movement of said valve and having an end spaced from said seat, so that said valve must move in its direction of opening movement a substantial distance before moving past said end of said wall, there being a ilow restricting clearance between said valve and said wall lwhen said valve is between said seat and said end of said wall.

2. In a standing valve assembly for a free well pump, the combination of: a valve body providing a seat and providing a cylinder coaxial with said seat and having an open end, said valve body also providing a cylindrical wall adjacent and coaxial with said seat and having an end spaced from said seat; and a valve in said valve body and movable downwardly under the iniluence of gravity from an open position above said wall past said end of said wall and into engagement with said seat, there being a flow restricting annular clearance between said valve and said wall, said valve having a stem which extends into said open end o-f said cylinder and which cooperates with said cylinder to provide a closed chamber of variable volume, said stem having a diameter of the order of magnitude of 0.010 inch less than the diameter of said cylinder -to provide therebetween an annular ow restricting clearance which communicates with said closed chamber to restrict fluid flow into and out of said closed charnber, said annular clearance between said stem and said cylinder and said annular clearance between said valve and said wall retarding closing movement of said valve.

3. In combination: a well pump of the reciprocating type including reciprocable piston means and having an inlet for well fluid, there being no flow of well uid into said pump through said inlet at least during intervals when the direction of movement of said piston means is being reversed at the ends of the stroke of said piston means; means for reciprocating said piston means; a standing valve assembly including a standing valve seat in fluid communication with said inlet and a standing valve movable downwardly under the influence of gravity into engagement with said standing valve seat; and dashpot means for hydraulically retarding gravity-induced movement of said standing valve downwardly toward said standing valve seat to a rate to prevent seating of 15 2,771,902

References Cited in the le of this patent UNITED STATES PATENTS 204,280 Baker n May 2S, 1878 2,646,752 Slater July 28, 1953 Winchester Nov. 27, 1956 

